Quick answer: Smoke from Canadian wildfires — roughly 850 fires burning nationwide, more than 180 of them in Ontario — has streamed into the U.S. Midwest and Northeast, pushing air quality into the Unhealthy range for around 100 million people. New York City climbed into the Unhealthy zone (AQI in the 170s–180s) this week, and parts of upstate New York hit "Very Unhealthy." Forecasters expect brief relief, another surge into the weekend, and real clearing once showers and thunderstorms move through. Until then, the single best thing you can do is keep the outdoor smoke out of your home and filter what gets in.
This is a live situation and the numbers move hour to hour. Check AirNow.gov for the reading at your exact location. Below is what's happening, what it means, and the indoor-air steps that actually help.
What's happening right now
A large outbreak of Canadian wildfires — concentrated in Ontario but burning across much of the country — has lofted enormous plumes of smoke southeast into the United States. Air quality alerts have covered well over a dozen states. Milwaukee recorded an AQI of 644 this week, more than double its previous all-time record, and cities from Chicago and Detroit to Philadelphia and Boston have all been under the haze. In New York, the metro area pushed into the Unhealthy category while Central and Western New York and the Eastern Lake Ontario region were rated Very Unhealthy.
New York City's emergency management office issued an air quality advisory, the state has posted health advisories, and the city has handed out free KN95 masks — the kind of response reserved for genuinely hazardous air.
What the AQI number means
The Air Quality Index runs 0–500. The band that matters this week:
| AQI | Category | What it means |
|---|---|---|
| 101–150 | Unhealthy for Sensitive Groups | Kids, older adults, and people with heart or lung conditions feel it first |
| 151–200 | Unhealthy | Everyone may feel effects; sensitive groups more seriously |
| 201–300 | Very Unhealthy | Health alert — the whole population is at risk |
| 301+ | Hazardous | Emergency conditions |
An AQI of 171, where NYC has been sitting, is squarely in the Unhealthy range. We break down exactly what that does to your body in what an AQI of 171 actually means.
When will it clear?
The short version: not by wishing. Wildfire smoke lifts when weather pushes it out. Forecasters expect a brief improvement, then a resurgence overnight and into Saturday, before showers and thunderstorms finally scrub the air — with conditions easing back toward the Moderate range by Sunday. Rain is the reset button. Until it arrives, the smoke reloads as new plumes arrive from the north.
What to do outside
- Limit or reschedule outdoor exertion — running, mowing, sports — especially for kids, older adults, and anyone with asthma, COPD, or heart disease.
- If you must be out for a while, a well-fitted N95 or KN95 (not a cloth or surgical mask) is what filters the fine particles.
- Keep car windows up and set the climate system to recirculate.
What to do inside (this is where you have the most control)
Most of the air you breathe today is indoor air, and that is the air you can actually clean.
- Close windows and doors. Seal the obvious gaps. The goal is to stop pulling smoke inside.
- Run your HVAC fan continuously (set the thermostat fan to "On," not "Auto") with a MERV 13 filter installed. MERV 13 captures at least 85% of PM2.5 — the exact particle size wildfire smoke is made of. Every pass through the system pulls more smoke out of your air.
- Add activated carbon if the smell is getting in. Particle filters catch the soot; a carbon layer adsorbs the gas-phase smoke odor. Our Odor & Smoke filters combine both.
- Make a clean-air room. For a bedroom or nursery, a portable HEPA purifier or a DIY Corsi-Rosenthal box (a box fan plus four MERV 13 filters) drops one room's particle count fast and cheap.
One caution: denser filters resist airflow. On a newer system this is a non-issue, but if you have an older furnace with a weak blower, don't leave a loading filter in for weeks during a smoke event — see does a high-MERV filter restrict airflow. During heavy smoke, check the filter more often; it loads faster than usual.
The filters that handle smoke
For whole-home smoke defense, MERV 13 is the floor and MERV 14–16 pulls ahead in the fine-particle band if your system can take it. Our Maximum Protection collection carries MERV 13 through 16, including carbon-layer options for smoke and odor — all made in the USA. Not sure of your size? The filter finder takes three clicks, and shipping is the same on 1, 2 or 3 packs, so it's worth stocking a few while you're changing them faster than usual.
Frequently asked questions
Does a furnace filter really help with wildfire smoke? Yes — a MERV 13 filter with the fan running continuously meaningfully lowers indoor PM2.5. It won't match a sealed HEPA purifier in one room, but it cleans every room the system serves. Full detail in air filters vs wildfire smoke.
Should I run the AC during a smoke event? Yes, set to recirculate (not fresh-air intake), with a good filter in place. It cools and filters at once. Avoid whole-house fans and window units that pull outside air in.
How often should I change my filter during heavy smoke? More often than usual — check a 1-inch filter every couple of weeks during a prolonged event, since smoke loads it fast and a clogged filter chokes airflow.
Is an AQI of 171 dangerous? It's in the Unhealthy range, where the whole population can feel effects and sensitive groups are at real risk. Reduce outdoor exposure and clean your indoor air.
Ironside makes American-made air filters in every standard size, MERV 6 to 16, shipped flat-rate nationwide — the same shipping on 1, 2 or 3 packs. Find your size and breathe better.